Safety posts are used as parts of a safety system, such as a safety barrier for placement on the ground or on a staircase or at some other place, or as an edge protection on a building during construction or renovation preventing workers or tools from falling down. They can also be used as scaffolding posts. A safety post is mountable in a post holder, which can be for example a particular support that is attached to or resting on ground or some other base, or a general element, such as a scaffolding frame element. When mounting and demounting the safety post it is convenient that it is easy to fit the safety post into and remove the safety post from the post holder. Several different types of locking devices, which lock the post to the post holder, having a snap-in character, have been developed.
In Japanese patent application JP 11152892 a handrail locking device of a snap-in type is disclosed. The locking device is arranged at an end of a tube of the handrail, and it comprises a lever that is biased by means of a spring towards a locking position. The lever has a lock protrusion extending through a first hole of the tube wall, and a release protrusion extending in an opposite direction through a second hole of the wall. The lever acts like a seesaw, i.e. it pivots about a pivot portion located between the protrusions. The biasing spring is positioned between the lock protrusion and the pivot portion and extends from the lever to the inner surface of the tube wall in the same direction as the release protrusion, i.e. opposite to the extension direction of the lock protrusion. Thus, the bias spring continuously forces the lock protrusion out of the first hole and, at the same time, forces the release protrusion out of the second hole. When mounted in a handrail receptacle the lock protrusion extends through a hole in the wall of the receptacle, thereby locking the tube of the handrail in the receptacle, and preventing accidental lifting of the handrail out of the receptacle. The end surface of the tube is supported on a stop pin extending inwards of, or through, the receptacle. Thus, the stop pin defines the vertical position of the tube in the receptacle in order to align the lock protrusion with the hole of the receptacle wall and to support the handrail.
When the tube has been mounted in the receptacle, the lock protrusion is engaged with the receptacle and prevents the handrail from being pulled out of the receptacle. In order to remove the handrail from the receptacle, the release protrusion is simply pushed in. Thereby the lever pivots about the pivot portion and the lock protrusion is retracted to a position where it resides in the hole of the wall of the tube and no longer protrudes from the outer surface of the wall. Thereby the lock protrusion is no longer engaged with the receptacle, and the handrail can be removed.
This prior art locking device is working with a good principle of a biased pivotable lever. However, it is disadvantageously dependent on the existence of the stop pin at the receptacle for supporting the tube and correctly aligning the locking device.
In Japanese patent application JP 09302922 a locking device is arranged at an end of first tube, and it comprises a lock element that is biased by means of a spring towards a locking position. The lock element has a lock protrusion extending through a first hole of the tube wall, and a release protrusion extending in the same direction through a second hole of the wall. The first tube is joinable with a second tube having a slightly larger diameter and having a lock hole in its wall. When joined the lock protrusion extends through the lock hole, and the end of the second tube abuts against the release protrusion. To demount the tubes, the release protrusion is simply pushed in. Thereby the lock protrusion is retracted to a position within the first tube. Thereby the lock protrusion is no longer engaged with the second tube, which can be removed. If there is a joining force, such as a force of gravity, when the lock protrusion is released the second tube moves a bit further onto the first tube, though only into a stop recession of the release protrusion.
A disadvantage of this prior art locking device is that there is no possibility of pushing the first tube further into the second tube in a simple way, which would be of interest in many situations.